Method for producing metals in blast furnaces



Patented July 3, 1951 METHOD FOR PRODUCING METALS IN BLAST FURNACES Emil Edwin, Oslo, Norway No Drawing. Application March 17, 1948, Serial No. 15,495. In Sweden April 3, 1947 1 Claim. 1

The invention relates to the production of pig iron in a blast furnace.

The constantly increasing difficulty of prccuring a suitable solid fuel for the production of iron in blast furnaces has caused inventors to (3.6 velop methods whereby the fuel consumption in these furnaces may be reduced.

Increase of the blasting temperature, enrichment of the blast with oxygen and many other means have been tried to achieve this end.

The oxygen of the oxidic iron ores charged into the blast furnace is, as generally known, discharged. from the furnace as a gaseous combination. The chemical equilibrium prevailing in these furnaces prevents the escape of the exhaust gases as a mixture of nitrogen and carbonic dioxide and these gases always contain a considerable percentage of carbon monoxide. As a coin sequence thereof and in addition to the production of the pig iron an essential generation of gases takes place in a blast furnace.

The conversion of solid fuels, which in some parts of the world are quite rare, into gas is often not desired. In the electrical blast-furnace the consumption of solid fuel can be considerably reduced; on the other hand, the greater portion of the electric energy is consumed by genera tion of gas, which greatly impairs the economy of this process.

It is obvious from the above that the hitherto customary production of high gas volume in the blast furnace is a considerable drawback.

A main object of the invention therefore consists in a reduction of gas creation in the blast furnace to a possible minimum.

It is another object of the same to control the blast furnace process in such a manner that this minimum of produced gas is mainly used for the metallurgical requirements of the iron production.

In order to comply with these objects suggestions were made to circulate the escaping gases through the furnace, to simultaneously remove the carbonic acid from the same and to heat the thus oxygen enriched gases to a temperature of between 1600 to 2000 C. These suggestions have never reached the stage of practical usability.

The above recited drawbacks of the art are eliminated by the invention, which is based on the following recognition.

Instead of increasing the oxygen content of the blast its nitrogen content is increased and a heated gas mixture is blown into the furnace, of which the oxygen content is less than 21%, for instance, 5-10 per cent, by volume. Due to the enrichment of the blast with nitrogen and the reduction of oxygen the coal combustion in the furnace is reduced and accordingly the combustion temperature. Therefore the necessity arose to heat the nitrogen-enriched blast to a sufficiently high temperature to guarantee the progress of the furnace operation, which is a temperature of about 2000 C. and higher.

In View of the foregoing, a high-tension electrical reverberatory furnace is particularly suited for the performance of the invention as these furnaces enable a pre-heating of the gases to about 500 to 700 C. by the exhaust gases of the blast-furnace itself and at the same time enable the supply of the blast in a technically satisfactory manner at the above mentioned high temperature.

An extensive theoretical investigation of the nature of the blast furnace process by the inventor has proven that the same can be successfully performed with a nitrogen blast having a surprisingly small percentage of oxygen and that additional energy is only needed for carrying-out the metallurgical side of the process and for the making-up of certain inevitable sources of heat losses.

Modern progress in the metallurgical art has created the requirement for large quantities of oxygen. This oxygen is most economically produced by separation from air; at the same time large quantities of nitrogen are recovered as byproduct. The invention renders it possible to combine the blast furnace work with the air separating methods. This combination will render it possible to produce pig iron with an average consumption per ton of about 450 to 500 kilograms coke and a consumption of electric energy of 800 to 900 kw. hr., the energy for the production of the nitrogen and the oxygen being included in this expenditure.

As the same time a gas may be derived from the oxygen enriched furnace gas which is directly usable in an open hearth furnace. Moreover, the production of the blast furnace can be greatly increased by the invention.

3 4 I claim: UNITED STATES PATENTS In a method of producing pig iron in a blast Number Name Date furnace which includes charging into the furnace 88 480 Hinde Mar 30 1869 a mixture of iron ore and coke, the improvement 1 695953 Feud 1928 which comprises blowing into the melting zone 5 229o192 Karwajt Jul'y 1942 of the furnace a heated oxidizing blast which is at a temperature of about 2000 C. and which con- FOREIGN PATENTS sists essentially of oxygen and nitrogen, the oxy- Number Country Date gen being present in an amount sufficient to ren- 275 601 Great Britain Oct 25 1928 der the blast oxidizing and not more than 21 per 10 7221293 France 1932 cent by volume- 181,191 Germany Feb; 22, 1-905 EMIL EDWIN OTHER. REFERENCES REFERENCES CITED Transactions of the A. I. M. E, vol. 131, pages 15 85 and 86. Published in 1938 by the American In- The following references are of record in the me of this patent: stltute of Mlning and Metallurgical Englneers,

New York, N. Y. 

